Two of the three trendlines go the wrong way. Or, no: I was wrong, two out of three. I shoulda showed it before. Can't think of everything though, not all at once.

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Okay. I decided to look at this "Three Subsets" thing because I sort of expect to see the trendline show increase in the early years -- the 1950s when private debt was particularly low. Once it gets to its optimum level, though, any further increase in debt should drive economic performance -- and the trendline -- down. That's my thinking, anyway.

Well, maybe I was right, two out of three.

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This is just quick. Took the same annual data in the scatterplot we looked at for a week and more, got rid of the one overall trendline, and added trendlines for a series of 5-year periods:

Graph #4: Many Subsets

It is close to half-and-half. About half the trendlines are up-sloping, and half down-sloping. I guess, with scatterplot points all over the place, and an arbitrary chopping-up of the series, that is to be expected.

Still, the bigger, steeper up-trends occur at low levels of the P2P ratio, and none occur at high levels. There is only one down-trend for ratio values below 3.5, and it is all downtrend at high ratio values. These observations suggest, once again, that the low P2P is better for GDP growth than the high P2P.

Overall, taking all the trendlines as one general movement, that movement is down to the right: less growth of real GDP as the ratio of private to public debt increases.